Technical innovations and changes in the regulations relating to the equipment used in the sport of table tennis have had a major impact on the sport, affecting the outcome of many high profile tournaments, including the World Championships. In particular, there have been many technological improvements made to the table tennis racket and its two main components--the rubber and the blade--since the formal organization of the sport by the International Table Tennis Federation (ITTF) in 1926 (the ITTF is still the world governing body). Modern table tennis rackets have an "inverted rubber" (also referred to just as "rubber") which consists of a top sheet made of vulcanized rubber that is bonded to an inner layer of expanded rubber sponge or foam. The rubber is adhered to optimized wood or wood-composite blades. The playing characteristics of modern table tennis rackets bear little resemblance to the rackets employed in the 1920s or, for that matter, even those used in the 1950s. A world class player can produce shots with ball speeds up to 100 miles per hour and ball spins of up to 9000 revolutions per minute using modern equipment.
In the late 1970s a number of European table tennis players discovered that certain types of adhesives affect the playing characteristics of the rubber. These players would remove the rubber from the blade a short period prior to playing a match and then "reglue" (a commonly employed term in the sport of table tennis) the rubber onto the blade using glues based on solvents such as trichloroethylene and 1,1,1-trichloroethane. Prior to this regluing innovation, the only time a sheet of rubber was glued on was when an old worn out rubber sheet was to be replaced, or about every three to six months. Most of the glues employed were the types used to repair inner tubes of bicycles and automotive tires, the cold one-part vulcanizing fluids. Players found that with so-called "speed glued rubber," they could produce shots with increased speed and spin compared to rubber put on the racket with traditional rubber cements previously employed in the sport. The main disadvantages of speed glue were that the high performance effect lasted only a few hours and the rubber had a shorter playing lifetime than those glued on once with the traditional rubber cements.
The first players to exploit the benefits of the speed glue effect were the European players from Yugoslavia and Hungary, including I. Jonyer, T. Klampar, G. Gergely and D. Surbek. According to Rufford Harrison, Chairman of the ITTF Equipment Committee, Dragutin Surbek of Yugoslavia is given the major credit for popularizing this practice from 1979 to 1983. Surbek was World Doubles Champion in 1979 and 1983. Many coaches and world-class players attribute the dominance of the European players in the World Championships from 1989 to 1993, when Sweden won three World Team Titles, to the discovery of the speed glue effect. The previous twenty-year dominance by the Chinese players thus came to an end. In fact, the European success, based on the use of speed glue, was so resounding that many, if not most, of the modern Chinese players began to emulate the European style.
Numerous speed glue products based on the above solvents, and others such as toluene, were produced during the 1980s and the early 1990s by table tennis manufacturers. However, in 1992 and in the years ensuing, the ITTF decided to phase out the use of certain solvents because of health considerations. By early 1995, the ITTF prohibited the use of the following solvents and solvent types in table tennis glue: all halogenated solvents; all solvents with benzene rings; and N-hexane. In addition, the ITTF established a policy of randomly testing players' rackets in major international tournaments to determine whether the glue met ITTF regulations with regard to the banned solvents. In the 1995 World Championships, Kim Taek Soo of Korea was the first player in the history of the sport to be disqualified for using illegal glue after he had won his quarterfinal match.
Many players throughout the world continue to use speed glues based on ITTF-banned solvents in minor and major tournaments because the performance of the current ITTF-approved speed glues is inferior. In the U.S., for example, most table tennis dealers continue to sell speed glues with illegal solvents such as trichloroethylene, which is a very difficult solvent to obtain in Europe. Further, many players are able to purchase glues and solvents designed for other markets. Cold vulcanizing fluids for automotive tire repair and cigarette lighter fluids are two common products used by players who re-glue.
Numerous players who have based their game on the now illegal speed glues find themselves unable to compete against other playing styles with the currently approved table tennis glues. In the 1995 World Championships all four finalists were Chinese, an unexpected result considering the world rankings of the top European players. The style of play used by certain Chinese players was not affected as much by the change in performance associated with the new breed of ITTF-approved speed glues. In 1993 and 1994, the English Table Tennis Association (ETTA) went even further than the ITTF by banning all solvent-based speed-glues. The player outcry was so great that the ETTA reversed itself in 1995 and allowed the ITTF-approved speed glues to be used in tournaments, ostensibly because English players found themselves at too great a disadvantage in international tournaments.
Estimates concerning the change in performance of the new approved glues compared to the old ones vary. One reason for this is that the performance depends, at least to some degree, on playing styles. A common figure offered by world class players is that the best currently approved glues boost performance by about 15% in both speed and spin compared with non-speed glued rubber. This can be compared with a 30% boost associated with the old (now prohibited) speed glues.
Christian Lillieroos, a USATT Certified National Coach and National Coach of the United States Para-Olympic team, recommends that, in order to get the maximum performance out of the new breed of speed glues, players must pre-glue the sheets before playing approximately four or five times. After a few more reglues the glue buildup is so great as to affect the performance of the rubber. Eventually, the solvents in the glue cannot penetrate the solid rubber buildup on the back of the sponge. Without the solvent action on the sponge the speed glue effect generally is eliminated. In addition, with each successive application of glue, the weight of the rubber sheet is increased. Beyond a certain weight, the sheet must be discarded as the overall racket weight becomes too heavy for the player to use. Alternatively, the player can attempt to remove the glue buildup by various means, a very messy and not always successful process.
In order to reduce the amount of rubber build-up on the sponge, many players employ an ITTF-legal speed glue for three or four speed gluings and then switch to a blend of illegal solvents which provides improved performance without adding to the weight of the sheet. However, there have been a number of problems associated with the use of these illegal solvents, aside from the fact that they are not permitted for use by the ITTF. First, the degree of tack remaining on the rubber after using a solvent blend is not always sufficient to re-attach the rubber to the wood surface of the blade. Second, the performance is not consistent from one gluing session to the next. One possible explanation for this is that the illegal solvents currently employed for this purpose may degrade the built-up rubber layer covering the sponge so that the interface has diminished dynamic properties. Finally, at this time no manufacturer has had a pure solvent blend approved for use by the ITTF.
Once an adhesive system is applied to a rubber the player must decide when to attach it to the face of the blade. Some players choose to put the glue on when it is wet, others when it is dry, and still others wait until some degree of tack is present. A speed glue or non-speed glue also generally is used on the blade. The adhesive bond is considered to be based on a contact cement. As a consequence of the swelling of the sponge by the solvents in the speed glue, the sheet of rubber often curls upwards from the blade to such an extent that the rubber sheet does not adhere over its entire surface to the blade. Virtually all speed glues will curl the rubber to some extent. In fact, the degree of curl is used by players as an indicator of the potential performance of the sheet. Significant curling is a serious problem for a player as the performance of the sheet will be impaired. A number of the illegal and legal glues exhibit a tendency to have insufficient adhesive bond strength to adhere the curled sheet flat on the blade.
The length of time that a speed glue effect lasts and the consistency of its performance over a time period are critical parameters for a player. Many tournaments last for twelve hours or more. With the best prohibited speed glues, players have to reglue every two to three hours. Players therefore must reglue up to six times a day. In addition, there is a waiting period before one can use a speed-glued racket as it takes a certain amount of time before the full effect is present. With the new breed of ITTF speed glues the effect is generally longer, up to about five hours or more. This is certainly one of the main advantages of the new speed glues for the average player. However, for the World Class Player the maximum effect from the allowed glues is only an hour long, barely enough time to complete a long match (assuming a thirty-minute warmup period prior to the match). Also, the waiting period before the speed glue effect is present is somewhat longer (up to one hour) than with the prohibited glues (approximately 30 minutes). Therefore, it is difficult for the player to achieve consistent performance from the equipment in tournament conditions which often have unpredictably scheduled events.
The following summarizes the disadvantages of the present ITTF-approved speed glues: (1) their speed/spin performance characteristics are below the original, and now prohibited, trichloroethylene, 1,1,1-trichloroethane, toluene, hexane, etc. based glues; (2) they require an initial thick layer of glue to achieve maximum performance; (3) they typically employ a relatively high amount of solids which contributes to premature glue buildup problems and reduced rubber lifetime; and (4) the speed-gluing process can be an art which requires that players have a considerable base of personal experience and knowledge.
Although the prohibited speed glues previously set the standard for the industry, they also have disadvantages. These can be summarized as follows: (1) they employ potentially harmful solvents, many of which have been banned altogether for health and environmental reasons in certain parts of the world; (3) the speed glue effect lasts for only 2 to 3 hours; and (3) although they dramatically increase the speed, spin, and for some shots the control of the table tennis rubber, for some players control is difficult to maintain.